1. Field of the Invention
Embodiments described herein relate generally to a driving device which drives a lens and an image pickup device in a direction intersecting at right angles with an optical axis to correct a blurred image, and an image instrument such as a camera comprising this driving device.
2. Description of the Related Art
Recently, digital cameras capable of obtaining not only still images but also moving images have been on the market. Some of the digital cameras of this type have what is called a shake correction function to drive a movable frame which holds some of lenses constituting an imaging lens and an image pickup device in a direction intersecting at right angles with the optical axis of the imaging lens and thereby correct camera shaking by hand.
It is preferable that a driving device which drives the movable frame precisely and stably drives the movable frame for accurate correction of the shake. On the other hand, it is preferable that the driving device consumes a small amount of electricity because the shake correction is always working while the camera is active. It is also preferable that the driving device is small and light so that the camera is small and light.
A driving device known as one such example comprises three balls intervening between a movable frame and a fixed frame, a plurality of tension springs which pull the movable frame toward the fixed frame to press the three balls, and a set of voice coil motors (VCM) which drive the movable frame relative to the fixed frame in a direction intersecting at right angles with the optical axis.
However, in the conventional driving device described above, a plurality of tension springs are located outside a triangle that connects the centers of the three balls. Therefore, particularly when the tension springs differ in resilience due to manufacturing variation and assembly variation, the balance of press forces applied to the three balls by the movable frame and the fixed frame is lost, and the holding of the movable frame tends to be unstable. In the worst case, part of the movable frame may rise and precise drive control may be difficult if the variation of the tension springs is great.
Moreover, the conventional driving device described above requires a space to place a plurality of tension springs outside the triangle that connects the centers of the three balls, and therefore has a larger device configuration. Naturally, the mass of the movable frame is increased with the increase in device size, and a greater amount of electricity is consumed to drive the movable frame.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a driving device and an image instrument equipped with this driving device which permit stable and precise driving of a movable frame, a smaller device configuration, and lower power consumption.